diff --git a/common/config.go b/common/config.go
index eaf9caa02..772cd345d 100644
--- a/common/config.go
+++ b/common/config.go
@@ -45,6 +45,17 @@ func CheckUnusedConfig(md *mapstructure.Metadata) *packer.MultiError {
 	return nil
 }
 
+// ChooseString returns the first non-empty value.
+func ChooseString(vals ...string) string {
+    for _, el := range vals {
+        if el != "" {
+            return el
+        }
+    }
+
+    return ""
+}
+
 // DecodeConfig is a helper that handles decoding raw configuration using
 // mapstructure. It returns the metadata and any errors that may happen.
 // If you need extra configuration for mapstructure, you should configure
@@ -206,14 +217,3 @@ func decodeConfigHook(raws []interface{}) (mapstructure.DecodeHookFunc, error) {
 		return v, nil
 	}, nil
 }
-
-// ChooseString returns the first non-empty value.
-func ChooseString(vals ...string) string {
-    for _, el := range vals {
-        if el != "" {
-            return el
-        }
-    }
-
-    return ""
-}
diff --git a/common/config_test.go b/common/config_test.go
index e7cfe0627..9c8b42892 100644
--- a/common/config_test.go
+++ b/common/config_test.go
@@ -29,6 +29,33 @@ func TestCheckUnusedConfig(t *testing.T) {
 	}
 }
 
+func TestChooseString(t *testing.T) {
+	cases := []struct {
+		Input []string
+		Output string
+	}{
+		{
+			[]string{"", "foo", ""},
+			"foo",
+		},
+		{
+			[]string{"", "foo", "bar"},
+			"foo",
+		},
+		{
+			[]string{"", "", ""},
+			"",
+		},
+	}
+
+	for _, tc := range cases {
+		result := ChooseString(tc.Input...)
+		if result != tc.Output {
+			t.Fatalf("bad: %#v", tc.Input)
+		}
+	}
+}
+
 func TestDecodeConfig(t *testing.T) {
 	type Local struct {
 		Foo string